3.3V output power off?



  • Hello there,

    I use a WiPy but all pycom devices should be concerned.
    Is there a programming way to cut off power on 3.3V output? I mean, to switch off a connected device or probe when not using it?
    In my case, i have a probe which needs about 30mA when powered on. I would like to switch it off when not used by the main board to save a lot of battery power.

    Thank you! :)
    Jean



  • @robert-hh That is also my experience. There is a circuit quoted in the pycom docs at OEM MODULES/G01/DATASHEET pdf/page22. b2129764-468f-4b6a-a03f-9b7bc9647180-image.png which does the job.
    Note that there is an error in this dwg, and Q2 should be a P channel pwr fet such as the BSP170.
    When the gate of Q1 - which could be tied to a GPIO output - goes high, the 'active power' output will be at 3.3v.
    I use this circuit (with a P ch FET) to switch off the 3.3v to non essential devices when my G01 goes to sleep.



  • @John-Paul I've used the hold function to keep a couple of pins high during deepsleep John. I wired them is parallel & toggled them to inputs to switch the load off (to avoid the few microseconds of ugliness that might otherwise occur from switching them sequentially to outputs low). They easily handled 25mA without too much voltage droop.



  • @John-Paul As far as I know, there is no way to switch the 3.3V output. If you need that, you have to add an external switch, like a P-type Mosfet Transistor. If the power demands are low, you as well supply the external device by a GPIO output. Even if the ESP32 can supply 40mA at it's outputs, the voltage may be well below 3.3V then.


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